Local matrix metalloproteinase 2 gene knockdown in balloon-injured rabbit carotid arteries using nonviral-small interfering RNA transfection

Lysophosphatidic acid-induced vascular neointimal formation in mouse carotid arteries is mediated by the matricellular protein CCN1/Cyr61

Vascular smooth muscle cell (SMC) migration is an essential step involved in neointimal formation in restenosis and atherosclerosis. Lysophosphatidic acid (LPA) is a bioactive component of oxidized low-density lipoprotein and is produced by activated platelets, implying that LPA influences vascular remodeling. Our previous study revealed that matricellular protein CCN1, a prominent extracellular matrix (ECM) protein, mediates LPA-induced SMC migration in vitro. Here we examined the role of CCN1 in LPA-induced neointimal formation. By using LPA infusion of carotid artery in a mouse model, we demonstrated that LPA highly induced CCN1 expression (approximately six- to sevenfold) in neointimal lesions. Downregulation of CCN1 expression with the specific CCN1 siRNA in carotid arteries blocked LPA-induced neointimal formation, indicating that CCN1 is essential in LPA-induced neointimal formation. We then used LPA receptor knockout (LPA₁-/-, LPA₂-/-, and LPA₃-/-) mice to examine LPA receptor function in CCN1 expression in vivo and in LPA-induced neointimal formation. Our data reveal that LPA₁ deficiency, but not LPA₂ or LPA₃ deficiency, prevents LPA-induced CCN1 expression in vivo in mouse carotid arteries. We also observed that LPA₁ deficiency blunted LPA infusion-induced neointimal formation, indicating that LPA₁ is the major mediator for LPA-induced vascular remodeling. Our in vivo model of LPA-induced neointimal formation established a key role of the ECM protein CCN1 in mediating LPA-induced neointimal formation. Our data support the notion that the LPA₁-CCN1 axis may be the central control for SMC migration and vascular remodeling. CCN1 may serve as an important vascular disease marker and potential target for vascular therapeutic intervention.

Differential susceptibility of human primary aortic and coronary artery vascular cells to RNA interference

BACKGROUND

RNAi technology is a promising tool for gene therapy of vascular disease. However, the biological heterogeneity between endothelial (EC) and vascular smooth muscle cells (SMC) and within different vascular beds make them differentially susceptible to siRNA. This is further complicated by the task of choosing the right transfection reagent that leads to consistent gene silencing across all cell types with minimal toxicity. The goal of this study was to investigate the intrinsic RNAi susceptibility of primary human aortic and coronary artery endothelial and vascular smooth muscle cells (AoEC, CoEC, AoSMC and CoSMC) using adherent cell cytometry.

METHODS

Cells were seeded at a density of 5000cells/well of a 96well plate. Twenty four hours later cells were transfected with either non-targeting unlabeled control siRNA (50nM), or non-targeting red fluorescence labeled siRNA (siGLO Red, 5 or 50nM) using no transfection reagent, HiPerFect or Lipofectamine RNAiMAX. Hoechst nuclei stain was used to label cells for counting. For data analysis an adherent cell cytometer, Celigo was used.

RESULTS

Red fluorescence counts were normalized to the cell count. EC displayed a higher susceptibility towards siRNA delivery than SMC from the corresponding artery. CoSMC were more susceptible than AoSMC. In all cell types RNAiMAX was more potent compared to HiPerFect or no transfection reagent. However, after 24h, RNAiMAX led to a significant cell loss in both AoEC and CoEC. None of the other transfection conditions led to a significant cell loss.

CONCLUSION

This study confirms our prior observation that EC are more susceptible to siRNA than SMC based on intracellular siRNA delivery. RNAiMax treatment led to significant cell loss in AoEC and CoEC, but not in the SMC populations. Additionally, this study is the first to demonstrate that coronary SMC are more susceptible to siRNA than aortic SMC.

High throughput RNAi assay optimization using adherent cell cytometry

Background

siRNA technology is a promising tool for gene therapy of vascular disease. Due to the multitude of reagents and cell types, RNAi experiment optimization can be time-consuming. In this study adherent cell cytometry was used to rapidly optimize siRNA transfection in human aortic vascular smooth muscle cells (AoSMC).

Methods

AoSMC were seeded at a density of 3000-8000 cells/well of a 96well plate. 24 hours later AoSMC were transfected with either non-targeting unlabeled siRNA (50 nM), or non-targeting labeled siRNA, siGLO Red (5 or 50 nM) using no transfection reagent, HiPerfect or Lipofectamine RNAiMax. For counting cells, Hoechst nuclei stain or Cell Tracker green were used. For data analysis an adherent cell cytometer, Celigo^® was used. Data was normalized to the transfection reagent alone group and expressed as red pixel count/cell.

Results

After 24 hours, none of the transfection conditions led to cell loss. Red fluorescence counts were normalized to the AoSMC count. RNAiMax was more potent compared to HiPerfect or no transfection reagent at 5 nM siGLO Red (4.12 +/-1.04 vs. 0.70 +/-0.26 vs. 0.15 +/-0.13 red pixel/cell) and 50 nM siGLO Red (6.49 +/-1.81 vs. 2.52 +/-0.67 vs. 0.34 +/-0.19). Fluorescence expression results supported gene knockdown achieved by using MARCKS targeting siRNA in AoSMCs.

Conclusion

This study underscores that RNAi delivery depends heavily on the choice of delivery method. Adherent cell cytometry can be used as a high throughput-screening tool for the optimization of RNAi assays. This technology can accelerate in vitro cell assays and thus save costs.

Potential clinical applications of siRNA technique: benefits and limitations

BACKGROUND

RNA interference (RNAi) has become the method of choice for researchers wishing to target specific genes for silencing and has provided immense potential as therapeutic tools. This narrative review article aimed to understand potential benefits and limitations of RNAi technique for clinical application and in vivo studies through reading the articles published during the recent 3 years.

MATERIALS AND METHODS

Medline database was searched by using 'siRNA' or 'RNAi' and 'in vivo' with limits of dates 'published in the last 3 years', language 'English' and article type 'clinical trial' for obtaining articles on in vivo studies on the use of RNAi technique. Characteristics of clinical trials on siRNA registered at the http://www.ClinicalTrials.gov were analysed.

RESULTS

The only three clinical studies published so far and many in vivo studies in animals showed that the RNAi technique is safe and effective in treatment of cancers of many organ/systems and various other diseases including viral infection, arterial restenosis and some hereditary diseases with considerable benefits such as high specificity, many possible routes of administration and possibility of silencing multiple genes at the same time. Limitations and uncertainty include efficiency of cellular uptake, specific guidance to the target tissue or cell, long-term safety, sustained efficacy and rapid clearance from the body.

CONCLUSIONS

RNAi technique will become an important and potent weapon for fighting against various diseases. RNAi technique has benefits and limitations in its potential clinical applications. Overcoming the obstacles is still a formidable task.

siRNA applications in nanomedicine

The ability to specifically silence genes using RNA interference (RNAi) has wide therapeutic applications for the treatment of disease or the augmentation of tissue formation. RNAi is the sequence-specific gene silencing mediated by a 21-25 nucleotide double-stranded small interfering RNA (siRNA) molecule. siRNAs are incorporated into the RNA-induced silencing complex (RISC), which mediates mRNA sequence-specific binding and cleavage. Although RNAi has the potential to be a powerful therapeutic drug, its delivery remains a major limitation. The generation of nanosized particles is being investigated to enhance the delivery of siRNA-based drugs. These nanoparticles are generally designed to overcome one or more of the barriers encountered by the siRNA when trafficked to the cytosol. In this review, we will discuss recent advances in the design of delivery strategies for siRNA, focusing our attention to those strategies that have had in vivo success or have introduced novel functionality that allowed enhanced intracellular trafficking and/or cellular targeting. First, we will discuss the different barriers that must be overcome for efficient siRNA delivery. Second, we will discuss the approaches for siRNA delivery by size including direct modification of siRNAs (less than 10 nm), self-assembled particles based on cationic polymers and cationic lipids (100-300 nm), neutral liposomes (<200 nm), and macroscale matrices that contain naked siRNA or siRNA loaded nanoparticles (>100 microm). Finally, we will briefly discuss recent in vivo therapeutic success.